The wide acceptance of four pair unshielded twisted pairs (UTP) wire systems for data and voice transmission is due to the large installed base Electronic Industry Association (EIA) category 5 media local area network (LAN) systems. Demands on networks using four pair UTP systems, such as transmission rates, have increased, forcing development of industry standards for higher system performance than the EIA Commercial Building Telecommunication Wiring Standards 568A Category 5. The EIA 568A category 5 level performance defines electrical parameters for proper data signal systems that require up to 100 Megahertz (MHz) frequency bandwidth, i.e., fast Ethernet 100 Base-T. The latest data rates have increase up to 1000 mega-bits per second, 1000 Mbps (1000 Base-T Ethernet), that allow LAN systems to transfer data 10 times faster than 100 Base-T Ethernet on UTP media cabling. Because of the predicted sensitivity levels of transmitting up to 1000 Mbps, the EIA Commercial Building Telecommunication Wiring group has considered the implication of higher category levels for system electrical performance.
The EIA higher categories for cabling electrical performance will increase from level 5 to 5e (enhanced) and eventually to level 6. The electrical performance parameters, such as NEXT (near end crosstalk) and Return Loss and Attenuation, must be substantially lower than present EIA category 5 requirements. The highest bandwidth for the categories will probably increase from 1-100 MHz for category 5 to 1-200 MHz or more for category 6. For cabling systems to meet the anticipated higher electrical performance requirements, better cabling than standard EIA category 5 will be needed.
For any data transmission event, the received signal will comprise the transmission signal modified by various distortions. The various distortions are added by the transmission system, along with additional unwanted signals inserted somewhere between transmission and reception. The major unwanted signal, NEXT noise, has been one of the main issues in high speed cabling systems. NEXT noise is the major limiting factor in today's communication systems performance. Problems that arise from noise are data errors, system malfunctions and loss of the actual wanted signals. NEXT or crosstalk noise occurs when signal energy from one source is coupled to another victim line.
When one transmission pair (pair 1) is next to another pair (pair 3), crosstalk coupling can occur. The fields are either capacitively (electric), or inductively (magnetic) coupled, or both from pair 1 to pair 3.
Crosstalk in a communication system can be minimized by decreasing the signal's power, increasing the distance between signal lines, providing shielding between signal lines, and twisting the wire of a pair.
An RJ45 plug with EIA 568A T56BB wiring layout has an array of eight pins in order. Pins 4 and 5 provide the tip and ring pins of the first pair. Pins 1 and 2 provide the tip and ring pins of the second pair. Pins 3 and 6 provide the tip and ring pins of the third pair. Pins 7 and 8 provide the tip and ring pins of the fourth pair.
Crosstalk using the RJ45 plug will increase as the speeds or system transmission frequencies increase. Crosstalk generated in the cable is minimized by the transposition (twisting) of the transmitting pairs of wires. However, as the signal travels through untwisted sections, such as plugs and plug contacts, coupling occurs. In a differential balance two wire per pair transmission system, the signals that travel along each wire (media) of a pair are equal in amplitude but opposite in phase. The phase difference of the two signals is .+-.n radian or voltage +1(E1)=-voltage-1(E2) under ideal conditions. These signals, at any instantaneous time, couple electric and/or magnetic fields to adjacent lines which reduces their signal to noise ratio (S/N). The acceptable S/N ratio depends on the type or quality of service that is required by the system. To remove the noise components, a signal equal but opposite to the original signal is induced. According to Fourier's wave theory and Maxwell's theory of electromagnetic fields, coupling the opposite phase of the transmitted signal to a previously coupled adjacent line signal, the two signals cancel each other completely and therefore removes the noise from the adjacent line.
In the four pair connecting hardware system, multiple pairs are provided for data signal transmission. The worse case NEXT noise that a RJ45 plug creates is a balance coupled noise, meaning the noise is coupled equally upon the adjacent pairs. For an EIA T568B RJ45 plug, the worse case noise is typically between pairs 1 and 3, pins 4 and 5, and pins 3 and 6, respectively.
Previous low noise EIA category 5 connector designs used one section signal compensation systems which are good for category 4 and 5 cabling systems, but probably will not provide category 6 electrical performance. Additional reduction of the unwanted NEXT noises, created by the patch cord and cables, to a lower level that might be required for category 6 rated channel performance.